Brush and brush material



Nov. 21, 1967 v. K. CHARVAT BRUSH AND BRUSH MATERIAL 2 Sheets-Sheet 1 Filed Jan. 27, 1966 VERNON K. CHARI/AT m,mwmwlg ATTORN S Nov. 21, 1967 v. K. CHARVAT 3,353,200

BRUSH AND BRUSH MATERIAL Filed Jan. 27, 1966 2 Sheets-Sheet 2 INVENTOR VERNON K. CHARVAT ATTORNEYS United States Patent corporation of Ohio Filed Jan. 27, 1966, Ser. No. 523,399 23 Claims. (Cl. 15179) This invention relates generally as indicated to a novel brush and brush material and more particularly to power driven rotary brushes having improved brushing qualities measured in terms of work accomplished as expressed by the rate of stock removal or surface area of finish produced.

Power driven rotary brushes of traditional design may utilize a wide variety of brush filament material including wire bristles, Tampico fiber, plastic bristles such as nylon, horsehair, plastic coated wire or glass fiber filaments as disclosed in Peterson Patent 2,782,734. Such Well-known bristle materials may be retained or anchored in any of a variety of brush back constructions by conventional mechanical means because the demands on the work performed by these tools is light in character and almost of a superficial quality. As brushes are introduced to do more primary work however, where the result demanded is considerably more than a mere optical finish, brush specification determination has begun to involve considerations of structural strength and product dimensional precision. These requirements for power brushes have been developed despite the known limitations of presently available brush backs in which construction details and/or manufacturing process operations have always imposed significant limitations on the fill material such as size, geometric configuration, hardness and other quality and quantity considerations.

In view of the new field application possibilities, the power brushing art must be developed further to produce harder working rotary brushes which are also true precision tools adapted to be driven at high speeds under heavy pressure and having carefully trimmed and often ground working faces to produce specific predetermined effects upon the work rather than the usual overall average appearance effect. Despite the foregoing, it has been the common practice in the industry, when using wire as the brush material, to crimp or twist the filaments to disperse the stresses within the individual filaments to avoid stress concentration at or near the retaining means, thus minimizing the highly objectionable long wire breakage which is the most objectionable kind of brush wear since efficiency and safety are both deleteriously affected. Consequently, brush bristle materials and brush back constructions have to be coordinated to produce a brushing unit having an acceptable wear pattern, and this is of great practical importance as the amount and rate of wear influence the number of working points of the brush in actual contact with the work as well as the efiiciency of the contacting cutting tips since the number of cutting tips and the condition and position of such tips as they contact the work is a primary influence on the kind and amount of work performed.

Moreover, in wheel brushes and the like where the bristles extend generally radially from a central support, the density of brush fill material is necessarily less at the working face than where such material is secured to the support and accordingly it is diflicult to assure uniform spacing of the brush bristles ends to achieve a uniform brushing face having the desired yielding intertip support. In the past, crimping of the brush material has been used since crimped wires are able to nest together in the base and yet spread out in the working portion of the brush to develop some interwire support.

Crimping of the brush material, however, has certain ice substantial disadvantages which are attributable, at least in part, to the highly variable wire nesting which occurs and which is the basic cause for displacement of the Wires from the correct position. Any filament may, of course, be displaced in three directions and thus the bristles of a brush are constantly rearranged by the forces involved in brushing. Consequently, when power driven brushes utilizing crimped brush material, particularly wheel brushes, are rotated at high speed and brought into engagement with the work, all of the bristles tend to lengthen which is a result of the centrifugal force and the pull resulting from frictional engagement with the work. With these forces thus applied to each bristle, regardless of the previous condition or orientation, it produces a very wide difference in the amount of individual lengthening of the various bristles.

Moreover, it is not possible to assemble crimped wire into a brush without it becoming entangled which is a cause for further delayed rearrangement of the bristles, which accordingly contributes to the production of a brushing face which is constantly changing in that new protruding wires project beyond the nominal working face. The carefully trimmed brush face thus loses its precision and even its diametn'cal size and the action of the brush on the Work become correspondingly irregular. It may accordingly become necessary, for precision work, to regrind the brush face soon after initial use and periodically thereafter, depending upon the exact quality of the work to be done. The crimp in the wire is the source of the slack which results in radical changes in the brush face condition initially, and it is also the origin of the constant although smaller subsequent changes.

Moreover, due to the crimp in the wires, certain of the brush bristle ends will extend in the direction of rotation of the brush whereas other bristle ends will extend in more or less the opposite direction. Consequently, the bristles extending in the direction or rotation will tend to lengthen on contact with the Work and to dig or gouge the workpiece surface, whereas the bristle ends extending in the opposite direction will merely drag across the work surface. Furthermore, the bristles having tips orientated at a proximately to either the left or right of the plane of rotation will rotate slightly under contact pressure and assume a more neutral or dragging position where only ineffectual action may be obtained. The total effect of the crimped fill wire brush will thus be about 60% as etiicient as a brush filled with straight wire.

According highly important consideration is that hard brush bristle material is also usually fairly brittle and accordingly does not take a satisfactory crimp. Because of this, it is a practice of the industry not to harden wire which is to be crimped as much as wire which is to be used straight. Even if the crimping operation is adjusted to the harder Wire, its use in a brush is difiicult, if practical at all, because of the greater liability for increased stress concentration. It is accordingly an object of the present invention to provide a novel brush material utilizing hard straight wire and brushes including such material which have the qualities of interwire support and reduced stress concentration better than previously obtained by crimping but which are free from the disadvantages resulting from crimped wire in a brush.

It is an additional object of this invention to provide a brush material and brushes utilizing the same in which the double problem of modifying both the fill material and the construction of brush back is avoided and which permits full attention to be given to the fill material.

It is an additional object of this invention to provide a brush material and brushes utilizing the same employing hard bristle material, such as steel Wire having a Knoop hardness of 700 or greater without danger of excessive 3 long fracture of the bristles and consequent rapid disintegration of the brushin use.

A further object is to provide straight brush material and brushes utilizing such material in which hard wire bristles are used which are capable of undergoing selective embrittlernent during use.

An additional object is to provide brush bristle material having the indicated desirable characteristics which is relatively simple and inexpensive of manufacture within closely controllable tolerances.

Other objects, features and advantages of this invention will be apparent after a reading of the following more detailed description.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawings:

FIG. 1 is a side elevational view of .a typical rotary brush of the wheel type having radially extending brush material in accordance with this invention;

FIG. 2 is a fragmentary transverse cross-sectional view of the brush taken on line 22 of FIG. 1;

FIGS. 3 and 4 illustrate one form of the novel brush material of this invention, FIG. 4 being a cross-sectional view on line 4-4 of FIG. 3;

FIGS. 5 and 6 illustrate in closer detail the brush bristle material, FIG. 6 being a fragmentary enlarged view of the bristles of FIG. 5;

FIGS. 7 and 8 are cross-sectional views illustrating further embodiments of the bristle material;

FIG. 9 shows still another embodiment of the bristle material, and FIG. 10 is a cross-sectional view of a brush section utilizing the bristle form of FIG. 10;

FIG. 11 is a fragmentary plan view illustrating yet another form of the bristle material; and

FIG. 12 is a plan view of a modified brushing tool in which the novel bristle material is embedded or encapsulated in a body of elastomeric material.

Referring to the drawings and particularly to FIGS. 1 and 2 thereof, a typical rotary brush is illustrated designated by the numeral 1 which comprises an annular support2 and brush bristle material 3 which is secured within the support and extends generally radially outwardly therefrom. In this particular embodiment, the support includes an annular sheet metal brush back 4 of substantially U-shape cross-section and a retaining ring 5 within the brush back which securely retains the bristles therein. In this form, the retaining ring is also of a substantiallyU- shape or collapsed U-shape cross-section.

The brush bristles are shown more clearly in FIGS. 3 and 4 and as thus illustrated comprise straight hard wire bristles 6 bonded to bristles 7 of greater fatigue strength than the 'hard wire bristles by an elastomeric adhesive 8, which may be any suitable adhesive, such as, for example any of the commercial epoxy adhesives. One illustrative example of a suitable such material is that commercially available from Shell Plastics and Resin Division under the trade designation Epon R resin. This material is part of a heat curable resin system with an average molecular weight of about 350 to 500 and an epoxide equivalent of about 175-2l0 and is used with a curing agent such as mphenylenediamine, diaminodiphenylsulfone, hexahydrophthalic anhydride, boron trifiuoride monoethylamine or dicyandiamide, by preheating the resin to a temperature of approximately 130 F. and mixing with the curing agent.

The hard wire bristles suitable for use in this invention are preferably steel wires and will generally have a Knoop hardness of at least 600 and in some cases 700 or even in excess of 800. The Knoop. hardness test. is. a US. Bureau of Standards test in which micro-hardness is measured by means of a micro-indentation using a Tukon tester and hence is particularly suited to measure the hardness of fine filaments or other small or thin pieces. The diameter of the hard wires will normally be from about 0.008 to 0.090 inch, but the size of the wires may be varied as desired to accommodate the function of the particular brush. The second bristle is of greater fatigue strength than the hard wire bristle and may be a steel wire or a plastic monofilament such as nylon. The terminology greater fatigue strength is used herein as commonly understood in the industry and refers to the flexibility or resilience of the respective bristles; in general, the supporting ibristle should be capable of withstanding repeated flexing under working conditions without failure in use, whereas the harder wire will break promptly and cause long fracture. The diameter of the supporting wires may also vary depending upon the diameter of the working wires as well as upon the particular use of the brush and type of brush, but will normally be about 0.01 inch in diameter. In a preferred form, the smaller wire (the supporting wire) is approximately 50% smaller in diameter than the working wire.

Referring particularly to FIGS. 5 and 6, a preferred embodiment of the bristle material is illustrated. The hard wires have a plurality of serrations 9 spaced somewhat uniformly along the axial extent thereof. The serrations may extend about the complete circumference of the. wires or alternatively may extend only about a portion of the circumference. The form and size of the serrations may be varied but will be small in size, being of a dimension measured in parts of a thousand. For example, the mark or serration of the wire may be even less than 0.001 inch deep and need be only a few thousands of an inch long rather than being a groove extending completely about the wire. Similarly, the serrations may be spaced uniformly' or otherwise along the longitudinal extent of the Wire as sive fracture is relied upon to produce the desired regulated wire breakage which in turn produces a continuous supply of sharp wire ends or cutting tips for the brush. The serrations or notches in the hard wire bristles serve to produce a new cutting edge in a shorter time than if the Wlre is permitted to break at its own natural rate. Additionally, the serrations increase the brittleness of the wire hp and thus provide a character of fracture which maximizes the efiiciency of the cutting action and maintains the action for the maximum span of time by causing the wire to break frequently along its length with a sharp cut that does not round over quickly.

It should thus be noted that the present invention represents a distinct departure from the concept employed in previously known brushes, wherein the objective has been to avoid breakage of the wire bristles since it has been extremely difficult to provide for any degree of control of such breakage. In the present invention, however, bristles are provided in which the breakage is carefully controlled in length to achieve the highly desirable advan-- tages set forth.

To achieve the desired controlled breakage of the wires, the configuration and arrangement of the serrations or 1 notches may be varied, as previously mentioned, since a small notch or mark of the proper character will cause a structural element like a wire to break at a given point with considerably less than the ultimate load as compared to a similar structure with no notch present. Thus, it will be apparent that many and varied arrangements of serrations may be used, including opposed notches, notches which are positioned in a line on the wire, and a series of notches such as at, for example, 90, 120 and 180 displacement around the wire. The depth and length of the notches depends upon the character of the brushing work to be done, and especially upon the severity of the scouring action, which is related to the amount of material to be removed, since brushing work can vary from the removal of scale from hot rolled steel to the application of light surface finishin which is intended only to reduce highlights. The notch depth may be as much as the radius of the wire and the notch length may be equal to the diameter of the wire in certain applications, although normally both dimensions will .be very small.

' In addition to the described serrations or notches in the hard wire, it is desirable to subject such wires to an electroplating or other similar process to diffuse hydrogen into the metal throughout the length of the wires to facilitate the desired selective em-brittlement thereof. It is well known, of course, that hydrogen will readily diffuse into high carbon steel or cold-worked steel parts and when this occurs, embrittlernent will result. This has been a generally objectionable characteristic, however, in previously known brushes and brush materials since diffused hydrogen will produce uniform embrittlement of the wire and breakage will thus occur at the retaining member or other point of highest stress in the brush which shortens the life of the brush considerably without any gain.

In the present invention, hydrogen diffusion is combined with the previously described serrations in such a manner that selective embrittlement of the wire results. To achieve this, the hard wires are first electroplated or treated in some similar process such as a standard pickling wherein a source of hydrogen atoms is obtained. In this way, the hydrogen atoms are liberated and diffused throughout the volume of metal. After the hydrogen atoms are present, the wire is then deformed by the notching to cause the hydrogen atoms to migrate ahead of the stress areas. The hydrogen atoms thus are caused to collect at the grain boundaries and to form molecules. At such points, the molecules are unable to migrate further, and they accordingly build up pressure which in turn develops many tiny ruptures. In this way, the metal will lose its ductility in a selective manner. In the present invention, therefore, the bristles combine the concentration of stress at points where embrittlement is highest and Where there are minute ruptures or cracks which, under the normal forces of brushing, will propagate into desirable breakage in increments which provide a continuously sharp brush without a heavy penalty in terms of reduction in brush life.

As an example of a suitable pickling operation, the wires may be immersed in an acid bath consisting of, for example, an aqueous solution of about percent by volume of concentrated sulfuric acid and about 10 percent by volume of concentrated nitric acid. The bath is preferably at room temperature and the wires remain in the bath for from about seconds to about 4 minutes, after which they are rinsed with water and dried. The bath may also, if desired, be agitated to produce a good cleaning action.

In FIGS. 7 and 8, additional embodiments of the bristle material are illustrated. In FIGS. 7, the hard wire is depicted by numeral 10 and is bonded to the wire of greater fatigue strength 11 through elastomeric adhesive 12. In this embodiment, the bristles are of different diameters, with the hard wire being the larger of the two. In FIG. 8, the hard wire 13 and softer bristle 14 are completely encapsulated within an outer coating of elastomeric resin 15. It is to be understood that in both of these embodiments, the hard wire may, of course, have the serrations or notches previously discussed.

In the FIG. 8 embodiment, the outer coating of elastomeric resin may be any of a number of commercially available materials, such as polyvinyl chloride, poly- 6 urethane rubber, or a latex such as a Hycar latex. The preferred elastomers are the polyurethanes and particularly the foamed polyurethanes.

Referring to FIGS. 9 and 10, another form of brush bristle and brush construction are shown in which a plurality of lengths of hard wire bristles 16 and 17 are attached to bristle 18 of greater fatigue strength by elastomeric adhesive 19. The hard wire bristles are spaced axially along the bristle 18 so that a space 20 is provided where the bristles may be folded about a retaining ring 21 as shown in FIG. 10. Thus, the brush section comprises the annular brush back channel 22 with the bristles securely retained therein by the retaining ring about which they are folded in the region 20 and extend generally outwardly therefrom. This form of the invention has the additional advantage that it conserves room in the brush back and hence permits the use of a greater number of Working wires. The retaining ring is illustrated as being an annular solid ring, but it may also be a substantially U-shaped or collapsed U-shaped ring such as shown in FIG. 2 and described in Whittle Patent 2,288,337.

Another form of the bristle material is illustrated in FIG. 11 in which a hard Wire bristle 25 and a bristle 26 of greater fatigue strength are bonded together by means of axially spaced plastic beads 27. With respect to this form of bristle material, reference may be made to my U.S. Patent No. 3,090,061 for a disclosure of beaded wire bristles, such bristles ordinarily comprising elongated strands such as hard straight steel wire having elastic protuberances or beads bonded thereto at spaced intervals along the length of the wire. Such beaded brush material has proved highly successful in operation, and accordingly generally similar benefits may be obtained in the present invention through employment of the bristle material illustrated in FIG. 11.

When a relatively harsh brushing action is desired, elastomeric material may be intruded into the body of brush material, as in the embodiment illustrated in FIG. 12. The brush designated generally by numeral 28 has a central annular hub or support 29 with elastomeric material 30 being intruded into the body of bristles between the bristles extending substantially to the brushing face of the tool with only the extreme portions 31 of the bristles protruding therefrom. If desired, granular abrasive may also be incorporated in the body of elastomeric material which will be released at the working face of the tool as the latter wears back in use. Preferably, the body of elastomeric resin will be of a type adapted to erode at a somewhat greater rate under working conditions than the ends of the bristles themselves thereby to assure that the tips of the bristles will always be exposed to provide a more effective cutting action. Suitable elastorneric resins include neoprene, preferably with an appropriate foaming agent incorporated therein, certain polyester resins, polyurethane rubber and polyurethane foams.

It will thus be appreciated that the present invention has made it possible to provide high speed rotary brushmg tools utilizing hard and therefore very effective bristle material without decreasing brush life due to the long fracture thereof and without production of a non-uniform and hence inferior surface finish which would normally be anticipated when employing such materials.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in the following claims, or' the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A brush comprising a support and brush bristles secured thereto and extending therefrom, said bristles each comprising a straight hard wire bristle closely bonded to a substantially straight parallel supporting bristle of greater fatigue strength than said hard Wire bristle.

2 The brush of claim 1 in which said hard wire bristles have serrations therein spaced along the length thereof.

3,. The brush of claim 2 in which said serrations extend about the complete circumference of said hard wire bristles. V

4. The brush of claim 2 in which said hard wire bristles have hydrogen diffused thereinto throughout the length thereof.

5. The brush of claim 1 in which said hard wire bristles have a Knoop hardness of at least 600.

6. The brush of claim 1 in which said bristles of greater fatigue strength are wire bristles.

7. The brush of claim 1 in which said bristles of greater fatigue strength are plastic monofilarnents.

8 The brush of claim-1 in which said brush bristles are bonded together by plastic beads spaced along the longitudinal extent of such bristles.

9 The brush of claim 1 in which a body of elastomeric plastic is intruded between said brush bristles to em bed the latter.-

10. The brush of claim 1 in which said hard wire bristles have a diameter of from about 0.008 to 0.009 inch and said bristles of greater fatigue strength have adiameter of about 0.01 inch.

11. A brush comprising an annular sheet metal brush back of substantially U-shape cross-section, brush bristles within said brush back and extending outwardly therefrom, and a retaining ring securely retaining said bristles within said brush back, said bristles comprising straight hard wire bristles bonded to supporting bristles of greater fatigue strength than said hard wire bristles, a plurality of axially spaced lengths of said hard wire bristles being bonded to a single supporting bristle of greater fatigue strength whereby said bristles are folded about said retaining ring in the region of said bristles of greater fatigue strength between said axially spaced lengths of said hard wire bristles.

12. The brush of claim 11 in which said hard wire bristles have serrations therein.

13. The brush of claim 11 in which a body of elastomeric plastic is intruded throughout said brush bristlesf 14. The brush of claim 11 in which said retainingring is of substantially U-shape cross-section.

15. Brush bristle material for use in the manufacture ofpower driven brushes and the like comprising a straight hard wire bristle closely bonded to substantially straight parallel supporting bristle of greater fatigue strength than said hard wire bristle.

16. The brush material of claim 15 in which said hard wire bristles have serrations therein.

17. The brush material of claim 16 in which said hard wire bristles have hydrogen diffused thereinto throughout the length thereof.

18. The brush material of claim 15 in which said hard wire bristles are bonded to said bristles of greater fatigue strength by plastic beads spaced along the longitudinal extent of such bristles.

19. The brush material of claim 15 in which a plurality of axially spaced lengths of said hard wire bristles are bonded to a single bristle of greater fatigue strength.

21). The brush of claim 1 in which said supporting bristles are approximately smaller in diameter than said hard wire bristles.

21. A rotary brush comprising a large quantity of flexible filaments of high fatigue strength densely compacted together at their inner ends and extending radially outwardly of a common axis of rotation, and hard relatively brittle filaments bonded to said flexible filaments in close side-by-side relation thereto and extending inwardly from the outer ends of said flexible filaments only a portion of the length of the latter.

22. Brush bristle material comprising a flexible filament of high fatigue strength, and hard brittle filaments closely bonded thereto and extending from the respective ends thereof toward the longitudinal mid-point of said flexible filament, the opposed ends of said hard filaments being substantially spaced apart.

References Cited UNITED STATES PATENTS 2,207,156 7/1940 Neville et al. 15.1 59 X 2,504,330 4/1950 Henley 15-159 2,984,053 5/1961 Peterson 5 159.l 3,134,122 5/1964 Charvat 15.-179 3,239,867 3/1966 Charvat 1s- .179

CHARLES A. WILLMUTH, Primary Examiner.

PETER FELDMAN, Assistant Examiner. 

15. BRUSH BRISTLE MATERIAL FOR USE IN THE MANUFACTURE OF POWER DRIVEN BRUSHES AND THE LIKE COMPRISING A STRAIGHT HARD WIRE BRISTLE CLOSELY BONDED TO SUBSTANTIALLY STRAIGHT PARALLEL SUPPORTING BRISTLE OF GREATER FATIGUE STRENGTH THAN SAID HARD WIRE BRISTLE. 